This invention relates to a core for use in a casting mould, and is particularly, although not exclusively, concerned with a ceramic core for use in a mould for casting aerofoil components such as turbine blades and stator vanes of a gas turbine engine.
Stator vanes and blades in turbine stages of a gas turbine engine are commonly provided with internal cavities and passages to allow the flow of cooling air within the component. The blades and vanes may be made by casting, and the cavities and passages may be formed at least partially by positioning a ceramic core within the casting mould. More specifically, such components may be made by a form of investment casting known as the “lost-wax” process. In the lost-wax process, a wax pattern of the component to be cast is formed by injection moulding, around the ceramic core. The wax pattern, including the core, is then dipped into a ceramic slurry, which is then dried. The dipping process is repeated until an adequate thickness of ceramic has been built up, after which the ceramic mould is heated to melt the wax, which is removed from the mould interior. Molten alloy is poured into the mould. When the alloy has solidified, the mould is broken and the ceramic core is removed by leaching to leave the finished cast component.